Which fuel is more efficient petrol or diesel?

Diesel vehicles can often go between 20% and 35% more in a gallon of fuel than their gasoline counterparts. According to Bell Performance and Road and Track, customers who drive many miles on the highway tend to prefer diesel engines, as they are more efficient on these roads than gasoline engines. Diesel fuel simply contains more energy in each gallon than gas fuel, making it more economical overall. Diesel engines are still more efficient than gasoline engines, but less so for those who are mainly engaged in urban driving.

Diesel cars also have more torque, which translates into better fuel economy along with more impressive acceleration. A comparison between diesel fuel efficiency and gasoline doesn't even come close. Diesel engines tend to have 25% to 35% more fuel economy than gasoline engines. Diesel engines get a quarter to a third better “gasoline mileage” than gasoline engines.

A big part of the comparison between the diesel engine and the gasoline engine is the fuel efficiency figures. Diesel engines are simply better in this department, as much as 30 or even 40 percent better, although modern direct-injection gasoline engines are catching up. But that's not the whole story. Diesel engines are still much more efficient than gasoline engines in converting fuel into mechanical energy.

In fact, including the energy advantage of the fuel itself, diesel engines are up to 40% more efficient at doing so. Both types of engines are classified as “heat” engines because they convert the thermal energy of the fuel into mechanical energy. But diesel engines have better thermal efficiency than gasoline engines, which means they convert more of the heat into mechanical energy and waste less on the environment. Wait a moment and try again.

Diesel engines save more fuel than their gasoline counterparts. This is due to the fact that a diesel combustion cycle is more efficient (~ 36%) than a gasoline combustion cycle (~ 25%). Increased efficiency reduces fuel costs, which represent a significant part of a vehicle's running costs. The difference in fuel economy between gasoline and diesel engines is quite dramatic.

As a general rule, diesel cars use an average of 15 to 20% less fuel than their gasoline counterparts, especially on long motorway journeys. Using less fuel means that diesel engines also produce less carbon dioxide (CO), a key factor in the ongoing threat of climate change. When it comes to efficiency, diesel engines provide more efficiency by using 15-20% less fuel compared to gasoline engines. Low-end diesel engine torque provides a much better on-road driving experience.

However, the price of this efficiency is a higher premium compared to the gasoline variant of the same car. Parts and components for diesel cars are also often more expensive due to the complex construction of diesel engines. Diesel has changed; it has become widespread and has spread its small oily wings in many corners of the automotive market, with its offer of greater fuel economy (about a third better) and a greater range between filling stops an increasingly tempting proposition. So let's consider the example of the Tata Altroz, which is priced at ₹6,38,000 (Delhi for highway) for the base petrol version and ₹7,99,000 (Delhi for road) for the diesel counterpart.

Every time you park at a gas station, you've almost certainly noticed that diesel is more expensive per liter than unleaded gasoline. On the cutting and pushing of a windy road, or on a racetrack, they offer a very different experience than a petrol car, but they can still be fun and even competitive, as evidenced by Audi's success in the 24 Hours of Le Mans with diesel engines. The higher the compression ratio, the higher the combustion efficiency, the amount of fuel that is burned during combustion. However, gasoline engines tend to consume more fuel, which reduces fuel efficiency and increases fuel costs.

While running a gasoline engine with an air-fuel mixture that has the same stoichiometric ratio means that combustion efficiency is at its highest and emissions are at its lowest, it is not possible to do so without destroying the engine. For example, this allows a refinery to convert diesel fuel into gasoline fuel, based on gasoline demand. As seen above, both gasoline and diesel have very different characteristics and serve very different purposes, despite the fact that both are fuels for IC engines. On the other hand, gasoline cars cost less compared to their diesel counterparts due to less complex components.

Part of that success, of course, relies on the diesel car's ability to go further with a fuel tank, but more of that at a time. . .

Bethany Pesch
Bethany Pesch

Amateur music geek. Lifelong gamer. Incurable music trailblazer. Subtly charming organizer. Extreme internet evangelist.